This invention relates to a city water flushing and sludge prevention control method for use in a city water system having a plurality of street water mains interconnected by branch water mains and having hydrants connected to the branch water mains.
Maintaining and monitoring water quality is becoming increasingly important to most water utilities. In the United States, for example, the Safe Drinking Water Act amendments of 1986 have caused many water utilities to pay very close attention to the quality of water they are providing to their customers. Also, these new regulations require more sampling of the water from points out in the distribution system. These samples are taken on a regular basis and then tested.
U.S. Pat. No. 5,201,338 (herein incorporated by reference) discloses a system and device for flushing water mains and for taking samples from hydrants attached to the water mains. Although the ""338 patent can be used to flush water mains using the novel flushing hydrant described therein and to take water samples, there remains a very serious problem in flushing water mains using the flushing hydrant of the ""338 patent, other flushing hydrants, or fire hydrants.
The problem is best described by reference to FIG. 1, which shows the usual layout of a city water system.
In a city water system, street water mains M generally run down city streets and have a number of branch water mains B which have manual shut-off valves V1 and V2 and which interconnect the street water mains M1 and M2. In turn, buildings are connected to the branch water mains B. The branch water mains B also have fire hydrants H attached at various points.
It is known that sludge may accumulate in the branch water mains B unless they are periodically flushed. Flushing is typically done by opening hydrant H1 attached to a branch water main B. However, because of the path of least resistance, water will generally only flow from the street water main M1 closest to the branch water main B with the open hydrant H1, and not from the street water main M2 more distant from the branch water main B with the open hydrant H1. Therefore, the segment B1 of the branch water main B between street water main M1 and the hydrant H will be flushed, but the segment B2 between hydrant H1 and street water main M2 will not be flushed. Also, the attachment pipes between buildings and segment B2 will not be flushed.
Applicant has found that the buildup of sludge in the unflushed segments of the branch water mains B and the attached buildings can cause damage to copper pipes in the buildings if the sludge contains erosive materials.
There is a need for a sludge prevention control method that allows the segments B2 between the flushing hydrant H1 and the more distant street water main M2 to be completely flushed. There is also a need for a sampling apparatus that allows sludge to be detected and analyzed for erosive materials while the mains are being flushed.
For use with a city water system having a plurality of street water mains interconnected by branch water mains and having hydrants connected to the branch water mains, a city water flushing and sludge prevention method consisting of: inserting a sludge-prevention control valve into a branch water main between two street water mains and closer to one of the two street water mains; and closing the sludge prevention control valve, the sludge-prevention control valve in the closed position preventing water from flowing through the branch water main portion from the closer street water main during a flushing operation, whereby all water flows through the branch water main portion from the more distant street water main and thereby flushes the portion of the branch water main between the sludge-prevention control valve and the more distant street water main. The sludge prevention control valve can be opened and closed either manually or by an automatic control mechanism or any other way such as electrical, pneumatic, hydraulic, etc. Alternatively, an existing manual shut-off valve can be used instead of the sludge prevention control valve.
A principal object and advantage of the present invention is that it permits a segment of a branch water main that is not flushed by standard flushing operations to be flushed.
Another principal object and advantage of the present invention is that it thereby allows sludge to be removed from the normally unflushed segment and buildings attached to this segment.
Another principal object and advantage of the present invention is that this sludge removal helps to prevent damage to copper pipes caused by erosive materials in the sludge.
Another object and advantage of the present invention is that it may include a remote actuator attached to a fire hydrant which operates the sludge prevention control valve when the fire hydrant is opened for flushing the branch water mains.
Another object and advantage of the present invention is that it may include a fire department stop valve which prevents activation of the sludge prevention control valve by the remote actuator when high water pressure is desired, so that water to the hydrant comes from the street water main closest to the hydrant.